Many light-emitting devices utilizing an LED element include a combination of an LED element and a wavelength conversion material such as a fluorescent material in order to provide light emission with desired color such as white light emission. In general, such a wavelength conversion material can be dispersed in a sealing resin for the LED element to cover the LED element therewith. In a conventional production method, a substrate on which an LED element is mounted is provided with a recessed portion (horn), on the bottom of which the LED element is mounted. Then, a fluorescent material-containing resin is filled in the recessed portion to complete a light-emitting device.
In this light-emitting device, however, the optical path length from the LED element to the top surface of a portion of the resin layer immediately above the LED element may be different from the optical path length from the LED element to the peripheral side surface of the resin layer, resulting in color unevenness at those regions. For example, suppose a light-emitting device utilizing a combination of a blue LED element and a fluorescent material, bluish light can be observed at the area of the resin layer immediately above the LED element while yellowish light can be observed at the peripheral area of the resin layer due to the color of the light emitted from the fluorescent material.
To cope with this problem, methods for providing a hemispherical fluorescent material layer over an LED element by injecting a fluorescent material containing resin in between a mold and the LED element and curing the resin. (See, for example, Japanese Patent Application Laid-Open Nos. 2006-148147, 2008-211205, and 2010-125647.) In these methods, a compression molding method has been widely utilized as the resin molding method. Such a hemispherical fluorescent material layer can alleviate the color unevenness due to the difference in optical path lengths within the fluorescent material layer, but the effects are insufficient.
Further, in order to remove bubbles contained in the fluorescent material resin, the compression molding method may require inserting a thin releasing sheet in between a mold and a substrate on which an LED element has been mounted and perform vacuuming. As a result, the fluorescent material resin can enter the space between the substrate and the sheet, so that a thin resin layer can be formed on the surface of the substrate where the LED element has been mounted.
Accordingly, the light-emitting device produced by means of the compression molding method, in addition to the hemispherical resin layer (sometimes referred to as a hemispherical fluorescent material layer), a thin resin layer formed around the hemispherical resin layer can be formed to emit light by the excitation of the fluorescent material by the light from the LED element. Therefore, the surrounding area can be observed as being more yellowish than the hemispherical portion, resulting in color unevenness more. A light source utilizing an LED element is often used for an illuminating device or the like in combination with condensing optical components such as a lens. When light emitted from such a light source with color unevenness is projected by condensing optical components or the like, the color unevenness or color separation is made more explicit, thereby providing mostly or only uneven illumination. FIGS. 1A and 1B are a cross-sectional view of a white LED light-emitting device (light source) produced by a compression molding method, and a schematic diagram illustrating how the color separation of the projected light occurs. As shown in the drawings (in particular, see FIG. 1B), the area immediately above the LED element can be observed to be a rectangular bluish area corresponding to the shape of the element, the area surrounding the bluish area can be observed to be a white light area, and the area around the hemispherical resin layer can be observed to be a yellowish area.
To cope with this problem, after molding the resin layer, the thin resin layer around the hemispherical resin layer can be removed by sandblasting or peeled off by tape masking. However, when the thin resin layer is removed by sandblasting, the hemispherical resin layer may also be damaged at the same time. When the thin resin layer is peeled off by tape masking, the hemispherical resin layer may also be peeled off partially at the same time, resulting in decreased production yield of the light-emitting device.